Mainframe Interview Questions

While allocating KSDS Datasets, free space is declared at regular intervals at the time of initial loading. This is done because this free space is utilized for keeping the data arranged in sequence physically, even though inserted randomly.

The following commands are available for the Program Control services:

LINK: To pass control to another program at the lower level, expecting to be returned. XCTL: To pass control to another program at the same level, not expecting to be returned.

RETURN:  To return to the next higher-level program or CICS. 

LOAD: To load a program. 

RELEASE: To release a program.

DB2 precompiler (if embedded sql used), CICS translator (if CICS program), COBOL compiler, Link editor. If DB2 program, create plan by binding the DBRMs.

READNEXT reads the next record from a browse operation for any of the three VSAM files.

DeCLarations GENerator : used to create the host language copy books for the table    definitions. Also creates the DECLARE table.

Syntax:

SORT   file-1 ON ASCENDING/DESCENDING KEY key....

USING  file-2

GIVING file-3.

USING can be substituted by INPUT PROCEDURE IS para-1 THRU para-2

GIVING can be substituted by OUTPUT PROCEDURE IS para-1 THRU para-2.

file-1 is the sort workfile and must be described using SD entry in FILE SECTION.

file-2 is the input file for the SORT and must be described using an FD entry in FILE SECTION and SELECT clause in FILE CONTROL.

file-3 is the outfile from the SORT and must be described using an FD entry in FILE SECTION and SELECT clause in FILE CONTROL.

file-1, file-2 & file-3 should not be opened explicitly.

INPUT PROCEDURE is executed before the sort and records must be RELEASEd to the sort work file from the input procedure.

OUTPUT PROCEDURE is executed after all records have been sorted. Records from the sort work file must be RETURNed one at a time to the output procedure.

Primary key : a relational database constraint. Primary key consists of one or more columns that uniquely identify a row in the table. For a normalized relation, there is one designated primary key.

Unique index: a physical object that stores only unique values. There can be one or more unique indexes on a table.

EXEC CICS READ

DATASET('FILENAME')

INTO(data-area)

RIDFLD(data-area)

KEYLENGTH(1)

GENERIC

LENGTH(WK-LEN)

END-EXEC.